Food safety experts at Consumer Reports are advising people to stop eating romaine lettuce until federal authorities identify the cause of an E. coli outbreak that has sickened nearly 60 people in 13 states, including Pennsylvania.

The Public Health Agency of Canada has identified romaine lettuce as the source of an E. Coli outbreak in that country.

The Centers for Disease Control and Prevention has not identified the source of the infections in the U.S. In a news release last week, the CDC said “preliminary results show that the type of E. coli making people sick in both countries is closely related genetically, meaning the ill people are more likely to share a common source of infection.”

The CDC, however, did not recommend that U.S. residents avoid romaine lettuce or any other food.

Consumer Reports is calling on the FDA to issue a general warning so more people don’t get sick. It pointed out that lettuce is almost always consumed raw, and washing your greens won’t necessarily get rid of the bacteria.

Consumer Reports said the strain of E. coli produces a toxin that in some cases can lead to serious illness, kidney failure, and even death.

Young children, the elderly, and anyone with a weakened immune system are at greater risk.